Terms such as "forward", "rearward", "left", "right", etc when used in connection with the baler and/or components thereof are determined with reference to, and facing in, the direction of operative travel of the baler in the field.
In a conventional baler, as exemplified in U.S. Pat. No. 4,106,267, issued Aug. 15, 1978 in the name of Allen A. White, hay, straw, or similar crop material that has been previously cut, is picked up from the ground by a pickup unit, fed into a duct by a packer unit and loaded in successive batches or charges into an elongated bale chamber by tines of a stuffer unit in timed sequence with a reciprocating plunger. The plunger compresses the material into bales and, at the same time, gradually advances the bales towards the outlet of the bale chamber. As the bales reach a predetermined length, a knotter device is actuated which wraps twine or other flexible binding material around the bale and secures the ends thereof together.
The packer unit precompresses the crop material in the duct against a backstop formed by the plunger. The stuffer unit is designed to load charges of said crop material into the bale chamber within the interval during which the reciprocating plunger clears the entrance of the bale chamber. Typically this is accomplished by a fork assembly comprising arms rotatably connected to cranks, the arms being provided with longitudinally extending slots in which stationary journals are received. A uniform revolution of the cranks makes the arms shift along and pivot about the journals so that the tines of the fork travel in a generally kidney-shaped path with a varying speed. The maximum speed is attained when the distance between the connection to the cranks and the stationary journals reaches its minimum, since the arms then act as levers with very close fulcrum points. Such system permits a quick sweep of the material behind the packer unit through the duct and to the entrance of the bale chamber.
This White stuffer unit was originally designed for the baling of dry, low density material such as straw or hay, but recently there has been an important shift in some area from the use of hay to the use of silage. Silage grass can also be baled, but since it has a higher moisture content and therefor a higher density than dry crop materials, the load on the components of the stuffer unit increases accordingly. A stuffer overload protection, developed for the baling of straw or hay, will easily be triggered by the forces which occur during the baling of silage. A conventional protection is the use of a shear bolt in the drive line of the stuffer unit. When the loads exceed the shear force of the bolt, the stuffer is disconnected before its components are damaged. This system requires the operator to use valuable time to replace the sheared bolt and is most instances to clear the duct manually before the baler can be restarted.
Some of the forces which occur during the baling of silage can be reduced by applying a low friction layer to the inner surfaces of the duct, as described in U.S. Pat. No. 4,862,797, issued Sep. 5, 1989 in the name of Michel Mathis. This layer diminishes the friction forces of silage in the duct, but it does not cope with the effect of its heavier mass. Thus the larger inertia forces on the tines of the stuffer unit remain unchanged. Hence, the baler still is vulnerable to triggering of the overload protection by normal silage forces.